Multi-channel signals may be reproduced by three or more speakers, for example, 5.1 or 7.1 surround sound channel speakers to develop two-dimensional (2D) and/or three-dimensional (3D) effects.
Conventional surround sound systems can produce sounds placed nearly in any direction with respect to a listener positioned in a so called sweet spot of the system. However, conventional 5.1 or 7.1 surround sound systems do not allow for reproducing auditory events that the listener perceives in a close distance to his head. Several other spatial audio technologies like Wave Field Synthesis (WFS) or Higher Order Ambisonics (HOA) systems are able to produce so called focused sources, which can create a proximity effect using a high number of loudspeakers for concentrating acoustic energy at a determinable position relative to the listener.
Channel-based surround sound reproduction and object-based scene rendering are known in the art. Several surround sound systems exist that reproduce audio with a plurality of loudspeakers placed around the so called sweet spot. The sweet spot is the place where the listener should be positioned to perceive an optimal spatial impression of the audio content. Most conventional systems of this type are regular 5.1 or 7.1 systems with 5 or 7 loudspeakers positioned on a rectangle, circle or sphere around the listener and a low frequency effect channel. The audio signals for feeding the loudspeakers are either created during the production process by a mixer (e.g. motion picture sound track, music sound track) or they are generated in real-time, e.g. in interactive gaming scenarios or from other object based scenes.
FIG. 1 shows a well-known reproduction system which comprises a surround system with a number of loudspeakers 4.1 to 4.5 and at least two loudspeaker bars 5.1 and 5.2 arranged around a position X of a listener L in an environment 1, e.g. in a room, to reproduce audio signals, e.g. motion picture sound track, music sound track, interactive gaming scenarios, and thus an acoustic scene 2 for the listener L in the room: Whereas the surround system produces distant sound effects and the loudspeaker bars 5.1 and 5.2 produce the effects close to the listener L.
The document KR 100 818 660 B1 describes a 3D sound generation system for a model in a near field to improve the immersion for a virtual reality by modelling for a far ear and a near ear in the near field with a different method. A 3D sound generation system for a model in a near field includes a far ear processing unit and a near ear processing unit. The far ear processing unit processes a sound source reached in an ear positioned at a far side among the sound source generated in the near field. A high pass filter having a cut-off frequency of 2-5 KHz is included at the far ear processing unit for attenuating a high frequency. The near ear processing unit processes a sound source reached in an ear positioned at a near side among the sound source generated in the near field.
The document WO 2011/068192 A1 provides an acoustic space which realizes the movement of sound from inside the human body to outside of the human body, or reversely, from outside of the human body to inside of the human body. A sound output device mountable near the ear is used as the output means for internal sound positioned in the human head, and an externally located sound output device is used as the output means for external sound; the spatial effect of the sound is implemented as the acoustic space between inside and outside of the body. The acoustic conversion device is provided with a sound signal generation device, at least one internal sound output device mountable near the ear of a listener, and at least one external sound output device positioned at a distance from the listener. The internal sound output devices and the external sound output devices are capable of simultaneous output, and said devices output different sound information such that the listener can listen to sound from the internal sound output device and the external sound output device.